Your Mac won‘t start up in Mac OS X (Mac OS X 10.3.9 or earlier)

Nothing can be more frustrating than turning on your Mac only to find that it won't start up. Instead of seeing the Finder, you see a blue or gray screen, an icon of a broken folder, a kernel panic, a flashing question mark, or a computer that just sits there. What can you do? Don't worry. It could be a simple issue that you can fix yourself.

The first step to help your Mac start up again is to identify which symptom you see. Once you know what the symptom is, you can try to fix it. Here's a list of the most common things you might see if your Mac turns on but doesn't start up. Click the link for the symptom you see, then follow the steps to fix it.

Drag third-party items out of the /Library/StartupItems and /System/Library/StartupItems folders. You may wish to temporarily store them in the Mac OS X Users folder. If you're unsure whether an item is a third-party item or an Apple-installed item, don't move it.

If this resolves the issue, add the login items one at a time until the symptom occurs again. That way you'll know which one is incompatible. Repeat these steps and remove the incompatible item.

Selecting the "Connect automatically when starting TCP/IP applications" option in Network preferences can sometimes cause this issue. You'll need to delete the preference file that holds this setting. This is an advanced step that will reset all of your computer's network settings. You will need to reconfigure them in Network preferences to reconnect to the Internet or a network.

Tip: Instead of "[affected username]", type the username for your account, or the account that is experiencing this issue. For example, if the username is "theta," type:
cd /Users/theta/Library

Press Return.

Type: mv Preferences Preferences_old

Press Return.

Type: mv Caches Caches_old

Press Return.

Type: reboot

Press Return.

If you can now successfully start and log in, use the following steps to isolate the issue:

Open the Console utility. It's in the Utilities folder (/Applications/Utilities).

From the File menu, choose Open Log.

In the goto field, type: /var/log/system.log, then click the Open button.

From the Edit menu, choose Find.

In the Find window, type "parse failed" and click the Next button.

Look for log entries that are similar to the following:

{DATE} Dock[500] CFLog (0): CFPropertyListCreateFromXMLData(): plist parse failed; the data is not proper ISO-8859-1. The file name for this data could be: com.apple.dock.plist -- /Users/us/Library/Preferences/ The parser will retry as in 10.1, but the problem should be corrected in the plist. {DATE} trident crashdump: Crash report written to: /Users/us/Library/Logs/CrashReporter/Dock.crash.log

For each "parse failed" message that you find, remove the matching .plist file from the ~/Library/Preferences_old folder. The tilde "~" character represents your home folder.

Repeat steps s and t until you have removed all of the .plist files associated with "parse failed" messages.

In the Finder, rename the ~/Library/Preferences folder to "Preferences_new".

Rename Preferences_old to Preferences.

From the Apple menu, choose Log Out. When the login panel appears log back in.

Important: If the issue is resolved, stop here. Otherwise, skip to step 9.

Tip: Instead of "[affected username]", type the username for your account, or the account that is experiencing this issue. For example, if the username is "theta," type:
cd /Users/theta/Library

Type: mv Preferences Preferences_old

Type: reboot

Press Return.

If you can successfully login, use the following steps to isolate the issue:

Open the Console utility. It's in the Utilities folder (/Applications/Utilities).

From the File menu, choose Open Log.

In the goto field, type: /var/log/system.log , then click the Open button.

From the Edit menu, choose Find.

In the Find window, type "parse failed" and click the Next button.

Look for log entries that are similar to the following:

{DATE} Finder[500] CFLog (0): CFPropertyListCreateFromXMLData(): plist parse failed; the data is not proper ISO-8859-1. The file name for this data could be: com.apple.HIToolbox.plist -- /Library/Preferences/ The parser will retry as in 10.1, but the problem should be corrected in the plist. {DATE} trident crashdump: Crash report written to: /Users/us/Library/Logs/CrashReporter/Finder.crash.log

For each "parse failed" message that you find, remove the matching .plist file from the /Library/Preferences_old folder.

Repeat steps o and p until you have removed all of the .plist files associated with "parse failed" messages.

In the Finder, rename /Library/Preferences folder to Preferences_new.

Rename Preferences_old to Preferences.

From the Apple menu, choose Log Out. When the login panel appears log back in.

When a kernel panic happens, white text on a black background is drawn on top of the last video image on the monitor before the panic occurred. You may see a message that begins with a phrase like "Unresolved kernel trap".

Make sure the latest firmware for your computer is installed. Check Apple Downloads for the latest versions.

Disconnect all peripheral devices, except for the Apple keyboard and mouse. This includes ADB, serial, USB, FireWire, SCSI, and PCMCIA devices. If this resolves the issue, connect one device at a time, restarting after each one, until you've determined which device is causing the issue.

Remove third-party hardware upgrades such as memory (RAM), microprocessor upgrade cards, and PCI cards. If this resolves the issue, add back one item at a time, restarting after each one, to isolate the issue. Note: Apple does not provide technical support for Mac OS X when used with third-party microprocessor upgrade cards.